EP1042259A1

EP1042259A1 - Method for producing 1,6-hexanediol

Info

Publication number: EP1042259A1
Application number: EP98963560A
Authority: EP
Inventors: Boris Breitscheidel; Rolf Pinkos; Frank Stein; Shelue Liang; Rolf Hartmuth Fischer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1997-12-23
Filing date: 1998-12-10
Publication date: 2000-10-11
Anticipated expiration: 2018-12-10
Also published as: KR20010033479A; DE19757554A1; KR100510000B1; MY119693A; DE59803387D1; WO1999033773A1; JP2001527056A; ES2174528T3; CN1097038C; CA2305590C; US6407294B1; CA2305590A1; EP1042259B1; CN1272835A

Abstract

The invention relates to a method for producing 1,6-hexanediol by hydrogenating adipic acid esters and/or 6-hydroxycarboxylic acid esters in the gaseous phase at an elevated temperature and pressure in the present of chromium-free catalysts. Hydrogenation is carried out a) using catalysts containing copper, manganese and aluminium as essential constituents or in the presence of Raney copper; b) at temperatures of between 150 and 230 DEG C and pressures of between 10 and 70 bar; c) at a molar ratio of hyrogen to hydrogenating ester of between 150 to 1 and 300 to 1; and d) at a catalyst load of between 0.01 and 0.3 kg C3-ester per litre of catalyst and hour.

Description

Process for the preparation of 1, 6-hexanediol

Description 5

The invention relates to an improved process for the preparation of 1, 6-hexanediol by gas phase hydrogenation of adipic acid esters, 6-hydroxycaproic esters or mixtures thereof in the presence of chromium-free catalysts essentially containing copper, manganese and aluminum or of Raney copper under certain hydrogenation conditions.

WO 97/31882, Example 1, discloses mixtures of dimethyl adipate and methyl 6-hydroxycaproate in the 5 liquid phase at 220 ° C./220 bar in the presence of

To hydrogenate 70% by weight CuO, 25% by weight ZnO and 5% by weight A1 ₂ 0 ₃ catalysts with selectivities of over 99% (conversion 99.5%) to hexanediol. The disadvantage of this hydrogenation in the liquid phase is the high reaction pressure, which entails considerable investment costs for the hydrogenation systems. This disadvantage can be compensated for by hydrogenation in the gas phase, since in the case of ester hydrogenations generally significantly lower reaction pressures, for example pressures below 100 bar, are sufficient. A condition for the economic viability of such gas phase hydrations is, however, that the investment cost advantage is not wiped out by other cost factors. Therefore, a similar high hexanediol selectivity must be achieved in the gas phase hydrogenation as in the liquid phase hydrogenation.

30 It is the object of a process for the gas-phase hydrogenation of Adipmsaurediestern ^¬, 6-Hydroxycapronsaureestern or mixtures resulted from Adipmsaurediestern and 6-Hydroxycapronsaureestern m the presence of catalysts comprising predominantly copper to hexanediol to find the min at Cg ester conversions of -

35 least 90%, in particular at least 95%, hexanediol selectivities of at least 95%, in particular more than 98%.

It was known from Japanese laid-open publication S 64-85938 that dimethyl adipate or diethyl adipate at 160 -

40 to 250 ° C and 10 to 70 atmospheres and diester / hydrogen molar ratios of 1: 100 to 1: 590 in the gas phase in the presence of copper chromite catalysts to hydrogenate to hexanediol. Only in one of eleven patent examples is a hexanediol selectivity of over 98% achieved. In example 6, a hexanediol selectivity is achieved.

45 activity of 98.9% (sales 97.5%) achieved. However, the hydrogen / diester molar ratio of 457 leads to very high energy costs. After all, chromium-containing catalysts are over the toxicity of chromium is problematic. Deactivated catalysts must be safely deposited at high cost.

From U.S. 5,395,990, example 13, it can be seen that the

Gas phase hydrogenation of dimethyl adipate at 180 ° C and 62 bar, a hydrogen / diester molar ratio of 480 and a catalyst loading of 0.4 1 diester / l ι _Kata _ysator. s _t un _d ei ⁿ the presence of a copper (41.1 wt .-%), manganese (6.2 wt .-%) and aluminum (20.4%) of existing catalyst similar results as in Example. 11 However, for the gas phase hydrogenation of dimethyl maleate, which was carried out under the same conditions as in Example 13, no information is given on the butanediol selectivity.

From US 5,406,004, Example 13, is known, dimethyl adipate at 220 ° C and 62 bar, a diester / hydrogen mole - ratio of 248-383 and a space velocity of 0.4 1 diester / l _K ataiysator. hour in the presence of the catalyst mentioned in US 5,395,990, Example 13 to hydrogenate to hexanediol. No information is given about the hexanediol selectivity and the diester conversion. It is only noted that results similar to those in Examples 2-4 are obtained. However, these examples are not a pure gas-phase hydrogenation since the temperature of the reaction mixture leaving the reactor is below the dew point of the mixture.

When reworking Examples 13 in U.S. 5,395,990 and U.S. 5 406 004, it was found that the hexanediol selectivities were significantly below the 95% and 98% required here (comparative examples 14 and 15). Above all, there are two groups of by-products that are responsible for the lack of hexanediol selectivity:

a) 5-ring connections:

2-methylcyclopentanol (1), 2-methylcyclopentanone (2), cyclopentanol (3) and hydroxymethylcyclopentane (4), which can be formed from dimethyl adipate: H

(1) (2) (3) (4;

The methanol released in the gas phase hydrogenation of dimethyl adipate could act as a methylating agent.

Based on the sum of the 5-ring connections, e.g. found in Example 5 61% (1), 29% (2), 6% (3) and 4% (4).

According to the process of EP-A 251 111, even the formation of cyclopentanone becomes the main product when adipic acid diesters are formed at 300 to 345 ° C. in the gas phase over solid oxidic catalysts of elements of the 1st to 5th main group, the 1st to VIII. Subgroup of the Periodic Table of the Elements or Oxides of Rare Earth Metals, especially alumina.

Cχ ₂ and Cχ ₃ esters

By transesterification of 6-hydroxycaproate with

Hexanediol produces 6-hydroxy-caproic acid (6-hydroxyhexy1) ester (5).

0

HO-CH ₂ - (CH ₂ > ₄ -C-0- (CH ^ -CH ₂ 0H

(5)

Adipinsäureme- methyl (6-hydroxyhexy1) ester _(6.) Is observed at a significantly lower amount than _(. 5), the well is formed by transesterification of dimethyl adipate with hexanediol.

o o

CH ₃ O-C- (CH ₂ ) ₄ -C-0- (CH ₂ ) ₅ -CH ₂ OH

The molar ratio of (5) to (6) is approximately 90:10. The by-product (5), which dominates in terms of quantity, has a much higher molecular weight (MW 232) and thus a significantly higher boiling point than dimethyl adipate (.MG 174) and 6-hydroxycaproate (MG 146).

The more (5) and (6) are formed, the higher temperatures and / or amounts of hydrogen are necessary to bring (5) and (6) into the gas phase and to hydrogenate them. Separating (5) and (6) after the hydrogenation from the hydrogenation discharge and returning it is complex. Therefore, unless they are hydrogenated, both must be considered by-products.

The object already described is now achieved according to the invention with a process for the preparation of hexanediol by hydrogenation of adipic acid diesters and / or 6-hydroxycaproic acid esters at elevated temperature and pressure in the presence of chromium-free catalysts, the hydrogenation

a) using catalysts containing copper, manganese and aluminum as essential constituents or in

Presence of Raney copper,

b) at temperatures from 150 to 230 ° C and pressures from 10 to 70 bar,

c) at a molar ratio of hydrogen to hydrogenating ester of 150 to 1 to 300 to 1 and

d) with a catalyst load of 0.01 to 0.3 kg of Cg ester per liter of catalyst per hour.

It was surprising that the sum of the by-products of 5-ring compounds and Cg acid (6-hydroxyhexyl) esters was less than 5 mol%, in particular 2 mol% (based on the adipic acid and 6-hydroxycaproic acid esters used) to maintain and thus achieve a hexanediol selectivity of at least 95%, in particular at least 98%:

In the gas phase hydrogenation of methyl adipate and 6-hydroxycaproate, as already stated, the by-products 2-methylcyclopentanol, 2-methylcyclopentanone, cyclopentanol and hydroxymethylcyclopentanone are likely to be formed as secondary products of cyclopentanone-2-carboxylic acid methyl ester and cyclopentanone. These by-products are characteristic of the hydrogenation of Cg mono- and dicarboxylic acid esters. Therefore you will not observed in the hydrogenation of alpha, omega-C, C ₅ , C ₇ and Cs diesters. Their amount increases with increasing temperature.

In addition, high-boiling 6-hydroxycaproic acid (6-hydroxyhexy1) ester and adipic acid methyl (6-hydroxyhexy1) ester are formed in the gas phase hydrogenation of adipic acid diesters. They are hydrogenated with stei ^¬ gender temperature under increasing formation of the desired product hexanediol.

Surprisingly, it was found that the desired selectivity of 95% and 98% can be achieved despite the temperature countercurrent of the two by-product groups.

Furthermore, it was not foreseeable that the catalyst would achieve a long service life despite the by-product formation.

Furthermore, when using adipic acid diester / 6-hydroxycaproate ester mixtures prepared according to DE-A 19 607 954, which also contain numerous other compounds, it was surprisingly found that both high hexanediol selectivities and long catalyst lives were achieved.

Pure adipic acid esters, e.g. -C-C dialkyl esters, 6-hydroxycaproic acid esters, e.g. -C -C alkyl esters or mixtures thereof are used. It is preferred to use ester mixtures such as can be obtained in the esterification of carboxylic acid mixtures formed as by-products in the oxidation of cyclohexane to cyclohexanone / cyclohexanol with C 1 -C 10 alcohols according to DE-A 19 607 954. These mixtures can e.g. B. additionally contain Glutarsauredi - esters, 5-Hydroxyvalerιansaureester, 2-Oxo-capronsaureester and Dihydromuconsaurediester.

Methyl and ethyl esters of the above-mentioned carboxylic acids are preferably used as starting materials for the process according to the invention.

The hydrogenation takes place catalytically in the gas phase.

Suitable catalysts are chromium-free catalysts essentially containing copper, manganese and aluminum, which may additionally contain minor amounts of zinc, zirconium and / or silicon. These primarily include catalysts as described in EP 0 552 463. These are catalysts that are in the oxidic form the composition

Cu _a Al _b Zr _c Mn _d O _x

have, where a> 0, b> 0, c ≥ 0, d> 0, a> b / 2, b> a / 4, a> c, a> d and x is the number required to maintain electroneutrality per formula unit denoted by oxygen ions. Specifically, for example, catalysts of the compositions of approximately 70% by weight CuO, 20% by weight A1 ₂ 0 ₃ and 10% by weight Mn ₂ 0 _{3 come} into consideration.

According to EP 0 552 463, these catalysts can be prepared, for example, by precipitation of poorly soluble compounds from solutions which contain the corresponding metal ions in the form of their salts. Suitable salts are, for example, halides, sulfates and nitrates. Suitable agents are all agents which lead to the formation of insoluble intermediates which can be converted into the oxides by thermal treatment. Particularly suitable intermediates are the hydroxides and carbonates or hydrogen carbonates, so that alkali metal carbonates or ammonium carbonates are used as particularly preferred precipitants. The thermal treatment of the intermediates at temperatures between 500 ° C and 1000 ° C is important for the production of the catalysts. The BET surface area of the catalysts is between 10 and 150 m ² / g.

Alternatively, Raney copper can be used as the catalyst, which can be prepared in a manner known per se by treating copper-aluminum alloys with alkali metal hydroxides and is used in lumpy form.

The catalysts can be arranged in a fixed bed or a fluidized bed reactor. The hydrogenation can be carried out in a trickle mode or in a bottoms mode. At least as much hydrogen is expediently used as the hydrogenating agent and carrier gas so that starting materials, intermediates and products never become liquid during the reaction. The excess hydrogen is preferably circulated, a small part being used as waste gas for removing inerts such as. B. methane can be discharged. One reactor or several reactors can be used in series or in parallel. The hydrogenation temperature is 150 ° C. to 230 ° C., preferably 160 ° C. to 200 ° C., particularly preferably 170 ° C. to 190 ° C.

The reaction pressure is 10 bar to 70 bar, preferably 20 bar to 60 bar, particularly preferably 30 bar to 50 bar.

The molar ratio of hydrogen to the sum of the Cg esters used is 150 to 300, preferably 170 to 290, particularly preferably 180 to 280.

The catalyst loading is from 0.01 to 0.3, preferably 0.05 to 0.2, particularly preferably 0.05 to 0.15 kg to be hydrogenated Cg-acetate / l ι _Kata _{YSA or.} s _t and _d

The conversion, based on the sum of the hexanediol-forming

Cg compounds such as adipic acid diesters, 6-hydroxycaproic acid esters, caprolactone and di ydromuconic acid diesters should be over 90%, in particular over 95%.

The hydrogenation is conveniently carried out continuously. The hydrogenation outputs are preferably worked up by distillation after the condensation of the hydrogenation output.

The hydrogenation consists essentially of 1, 6-hexanediol and the alcohol corresponding to the ester group. Other constituents are, in particular, if ester mixtures prepared according to DE-A 19607954 are used, 1,5-pentanediol, 1,4-butanediol, 1,2-cyclohexanediols and monoalcohols having 1 to 6 carbon atoms and water.

If the conversion contained in the hydrogenation discharge is incomplete, it can be separated off by distillation and returned to the hydrogenation stage.

Examples

A) Hydrogenation apparatus:

The tests were carried out continuously in the hydrogenation apparatus shown schematically in FIG. 1. It consists of an evaporator (E), a 1.4 1-tube reactor (30 x 2000 mm) (R), two coolers Ci and C ₂ and a pressure separator (S) for extracting the condensable components from the hydrogen stream, one Recycle gas compressor (K) for recycling the recycle gas (3) and a discharge vessel (T) to collect the reaction discharge (4). Carrying out the experiments:

In Examples 1-12 and Examples 14 and 15, a CuO (70% by weight) / Mn ₂ 0 ₃ (10% by weight) / A1 ₂ 0 ₃ (20% by weight) catalyst from the company was used Südchemie (T4489) was used, which was activated in the reactor with hydrogen / nitrogen mixtures in a volume ratio of 1:99 to 100: 0 at 160 - 200 ° C. The catalyst zone was delimited at the top and bottom by a layer of quartz rings. Recycle gas was used in all cases, with 10% of the recycle gas (5) being discharged and replaced by the same amount of fresh hydrogen.

In Example 13, the Raney copper catalyst A 3900 from Activated Metals was used.

The Cg-ester starting compounds (1) were metered into the evaporator by means of a pump (P), where they were evaporated and mixed with preheated hydrogen (2) were passed in gaseous form into the reactor. The ester / hydrogen molar ratio was determined by weighing the amount of starting product fed in and measuring the hydrogen flows.

The hydrogenation discharge was weighed after the condensation. Its composition was quantified by gas chromatography using an internal standard (diethylene glycol dimethyl ether). Each test setting was operated without change for about four days, only then was the hydrogenation output analyzed.

Examples 1-12

In these examples, 500 ml of CuO / Mn0 ₃ / Al 0 catalyst were used. The work was carried out with pure adipic acid dimethyl ester (density according to the catalog from Aldrich-Chemie, 1994, Steinheim, page 36: d = 1.063).

In Example 12, instead of dimethyl adipate, a mixture of dimethyl adipate, dimethyl 6-hydroxycaproate and other esters prepared according to DE-A 19 607 954 was used. It consisted of 52.3% dimethyl adipate, 9.1% 6-hydroxycaproate, 5.2% caprolactone, 4.1% dimethyl dihydromuconate, 1.5% dimethyl succinate, 2.5% valerolactone, 2.2% 5-hydroxyvalerate , 2.7% 2 -Oxocapronεäureester and 6.4% dimethyl glutarate (all wt .-%). Example 13

Worked with pure dimethyl adipate. 500 ml of Raney copper were used as catalyst.

Comparative Examples 14-16

In these examples, example 13 from US Pat. No. 5,395,990 (comparative example 14) and example 13 from US Pat. No. 5,406,004 (comparative example 15: 220 ° C.; molar ratio of dimethyl adipate / H ₂ = 1: 248) were reworked. 150 ml of CuO / Mn ₂ 0 ₃ / Al ₂ 0 ₃ catalyst were used.

All test results are summarized in Table 1 below.

Hydrogenation of dimethyl adipate in the gas phase over catalyst T 4489

¹⁾ 2-methylcyclopentanol + 2-methylcyclopentanone + cyclopentanol + hydroxymethylcyclopentane

²⁾ 6-Hydroxycaproic acid (6-hydroxyhexyl) ester + adipic acid methyl (6-hydroxyhexyl) ester

³⁾ Two moles of hexanediol are formed from one mole of C ₂ or C ₃ esters in the hydrogenation

⁴⁾ Use of dimethyl adipate / methyl 6-hydroxycaproate instead of pure dimethyl adipate

⁵⁾ Use of Raney copper instead of T 4489

Claims

claims

1. A process for the preparation of 1,6-hexanediol by hydrogenation of adipic acid esters and / or 6-hydroxycaproic acid esters in the gas phase at elevated temperature and pressure in the presence of chromium-free catalysts, characterized in that the hydrogenation

a) using catalysts containing copper, manganese and aluminum as essential constituents or in the presence of Raney copper,

b) at temperatures from 150 to 230 ° C and pressures from 10 to 70 bar,

d) with a catalyst load of 0.01 to 0.3 kg

Cg ester per liter of catalyst per hour.

2. The method according to claim 1, characterized in that the catalysts additionally contain zinc, zirconium and / or silicon.

3. The method according to claim 1, characterized in that catalyst loads of 0.05 to 0.2 kg

Cg-acetate / l _Kata iysator- hour complies.

4. The method according to claim 1, characterized in that catalyst loads of 0.05 to 0.15 kg

C ₆ - Ester / l _{Ka a} ι _ysa goal hour.

5. The method according to claim 1, characterized in that one carries out the hydrogenation with molar ratios of hydrogen to C ₆ esters from 170 to 290.

6. The method according to claim 1, characterized in that the hydrogenation with molar ratios of hydrogen to

Cg star from 180 to 280.

7. The method according to claim 1, characterized in that one carries out the hydrogenation at temperatures of 160 ° C to 200 ° C.

8. The method according to claim 1, characterized in that one carries out the hydrogenation at temperatures of 170 to 190 ° C.

9. The method according to claim 1, characterized in that one carries out 5 the hydrogenation at pressures of 20 to 60 bar.

10. The method according to claim 1, characterized in that one carries out the hydrogenation at pressures of 30 to 50 bar.

11. The method according to claim 1, characterized in that mixtures of adipic diesters and 6-hydroxycaproic esters are hydrogenated.

12. The method according to claim 1, characterized in that 15 as starting materials Cχ-C mono- or dialkyl esters

6-Hydroxycaproic acid or adipic acid used.

13. The method according to claim 1, characterized in that the starting materials to be hydrogenated are ester mixtures such as

20 they are formed by esterification of carboxylic acid mixtures which are obtained as by-products in the production of cyclohexanol / cyclohexanone by oxidation of cyclohexane with gases containing oxygen.

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